Dental oven



March 25 1924.

v M2882@ E. MAGINNIS DENTAL OVEN Filed April 25 1921 2 Sheets-Sheet 2*Dave/Ziff @L m 7% im Patented Mar. 2,5, 1924,

AUNITED sTA'r-E-s EUGENE MAGINNrs, or EvANsroN, ILLINOIS.

DENTAL o-vEN.

Application iiled'April 25, 1921. Serial No. 464,150.

To all ywhom'vlt may concern.'

Be it known that I, EUGENE MAGINNIS, a citizen of the United States,residing aft Evanston, in the county of Cook and State of Illinois,lhave invented certain new and useful Improvements in Dental Ovens, ofwhich the following is a specification.

My invention pertains to features of novelty and advantage, bothstructural and functional, in furnaces or ovens particularly, thoughnot. restrictedly, in such appliances of relatively small size designedand adapted for dentists work.

More specifically, the invention relates to heating appliances of thisgeneral type and style intended for burning out invested models as inthe manufacture of meta-l inlay casting for teeth, provided by firstforming a wax or similar model of the filling to be supplied, encasingsuch wax model in a covering or investment of appropriate more or lessporous material, such as plaster of Paris, and heating the -tlaskconta-inin such model and its covering to cause thea sorption of the waxin the investment material, thereby forming a matrix or mold the exactshape and size of the tooth cavity to be filled into which the moltenmetal may be poured to form lthe desired inlay or casting.

The heating of the flask to eiiect the dissipation of the wax must becontrolled within iertain temperature limits, otherwise defectiveV andimproper results ensue.

Electrically heated furnaces or ovens have heretofore'been provided forthis work but they have provento be unsatisfactory because of lack ofadequate heat control, a though at first thought it would seem thatnofsuch undesired results would necessarily follow. y i

Accordingly my improved oven or furnace is heated by burning gas and nodiiiiculty is encountered in automatically controlling the flow thereofto govern and control the temperature developed. i `Such heat also byreason oflts distribution yquired reliable and safe results.

A further object and purpose of the invention is the provision orproduction of an oven of this character which `is simple in structure,economical to manufacture, and which may be operated satisfactorily bypersons more -or less unskilled.

ln order that those acquainted with this art may have a full andcomplete understanding of the invention and its various benefits andadvantages, l `have illustrated a preferred and desirable embodiment ofthe same in the accompanying drawings forming a part of thisspecification and throughout the several views of which like referencecharacters refer to the same parts.

In these drawings:

Figure l is a substantially central longitudinal vertical sectionthrough the novel oven;

Figure 2 is a horizontal section on line 2 2 of Figure 1, thethermometer and its lsupport being omitted;

Figure 3 is a horizontal section on line 3-3 of Figure l, the partsbeing viewed in the direction indicated by the arrows;. y

Figure 4 is a vertical cross-section on line 4-4 of Figure l; and AFigure 5 is an inverted plan view of the heat delector employed over theburner or it may be considered as a horizontal section on line 5-5 ofFigure 4, the parts being viewed from below as shown by the arrows.

By reference to these drawings it will be seen that the improved oven orfurnace comprises a main, sheet-metal housing or casing characterized asa whole 10, comprising feet or legs 11 on which the structure stands, abottom wall 12, end walls 13 and 14, a front wall 15, a back or rearwall 16,

and a top wall 17, the margins or borders of the metal sheets beinginterfolded at 18, 19 and 20 to properly unite the parts together as iscustomary in sheetmetal work.

-As is indicated, perhaps most clearly in Figure 3, the horizontalbottom or ioor plate 12 has a central hole 21 therethrough and also asmaller hole 22 at or -near each of the four corners of thehousing forthe admission and more or less even oruniform distribution of the outerair to carry on the combustion of the gas.

Similarly, the top plate 17-has a central aperture 23 for t-he'discharge of the products of combustion and a smaller hole 24,]'ustback of the aperture 23 for the accommodation of a. thermometer 25referred to hereinafter.

A horizontal partition or division sheetmetal wall 26 divides thehousing or casing into an upper and a lower chamber 27 and 28,respectively, such plate or wall being of less length than the'inside ofthe housing leaving spaces between its ends and the adjacent end wallsof the housing.

Such partition wall is held in place by being fastened to the front andrear walls of the housing by means of rivets and downt'urned ears 29 and30 on plate 26, the back edge of the plate being spaced away from therear wallof the housing as depicted in Figure 4.

A chamber 31 is formed inside of the upper compartment 27 referred to bymeans of a bent metal plate having a downtinned flange 32 (Figure 4)inside of and fastened to the front wall 15, a horizontal top wall 33equippedwith two ventilatingholes 34,

34 (Figure 1) and an aperture 35 (Figure VIl() 4) for the thermometer25, a rear vertical wall v36 spaced forwardly away from t-he back wallof the housing, a horizontal floor wall 37 above and spaced away fromthe partition wall 26, and a downwardly extended flange 38 disposed andfastened between the flange 29 and the front wall 15 of the housing.

Such compartment or chamber 31 also has sheet-metal end walls 39 and 40(Figure 1) positioned inwardly somewhat from the cor` responding endwalls of the outer housing I or casing.

Thus the several walls of the chamber 31 are spaced away from the wallsof the housing and division wall except the front wall of the former,which in register with such chamber has a door opening 41 and a hingeddoor 42 therefor, the lower chamber or cornpartment 28below thepartition wall having a front door opening 43 and a hinged door 44.

The lower compartment 28 houses a Bunsen-gas-burner 45 over and raisedabove t-he opening 2l by the feet of the burner which rest on the bottomwall 12.

A bent pipe 46 extending through a hole 47 in the end wall 14 connectssuch burner to an automaticfgas controller 48 coupled to the gas supplyby a pipe 49.

The flow of gas through the controller from the pipe 49 to pipe 46 isgoverned or regulated by a valve arm 50 fulcrunied inside the controllerat 51 and adapted to open and close'more'or less a port through themember 52 interposed between the two pipes.

The valve arm is under the influence of a coil expansion spring 53tending to rock the Varm in a direction to open the port or passtembeing externally threaded and screwed in a hole in the end wall 14 andheld tight in position by a lock nut 56, such stein also extendingthrough a hole in the wall y40. The left hand endl of the tube is closedby a threaded plug 57 to which is fixedly fastenedv an end of athermostatic rod 58 extended through the tube and stem and through anapertureV in the fulcrumed valve arm 50, being supplied with a nut 59onthe threaded end of the rod and having arounded part 60 bearing on theouter face of the arm. Y

Hence as the tube and rod vary relatively as to length due to slightvariations or changes in temperature, the position ofthe valve arm willbe controlled to maintain a substantially uniform flow of gas and anunvarying temperature in the furnace.

The position of' the nut on the rod may be modified or changed to varythe controlled temperature by turning an external finger 61 on a shaftin the wall of the controller, such shaft having a bent arm im engagingone of several notches or recesses in the nut. Y

A heat deflector or shield 64 spaced below the horizontal division walland located above the gas-burner, has marginal flanges 65 along itsopposite edges and is fastened to the elements 26 and 37 by means ofbolts 66 extended through holes in such members and in end lugs 67 ofthe shield. Y

Thus the intense heat generated directly above the burner is distributedmore evenly and prevents the Vupper. chamber from becoming undulyhea-ted locally.VV

Two, or any other desired number of, deck or platform plates V68 areemployed in the chamber 3l, each having flanges resting on the Vfloorplate 37, Vwhereby such elements 68 are held above the latter providingair spaces between them.

The thermometer 25 positioned inV the registered holes 24`and 35 restson an asbestos'blo'ck 69 on one or both of the deck plates, its upperportion extending out of the furnace where the reading of the height ofthe mercury column may be easily takenl and hence the prevailingtempera-ture in the chamber readily ascertained.

The one or more flasks 7 Ocontaining the invested models are positionedon and 'sup-.b ported by such deck plates and are heated the requiredperiod at theproper andvcon# trolled temperature to effect theabsorption or dissipation of the wax of the model, all

will be readily understood. y

The air for carrying on the combustion of the gas at the burner entersthe lowerchaniber or compartment through Ythe 'several per-A forationsorapertures 21, 22 and 47, the hot gases rising from the burner beingprevented from directly striking or coming in contact with the divisionor partition wall immediate-ly above the burner by reason of thepresence ofthe shield or deflector 64.

Such hot gaseous products of combustion flow up past the end and rea-rwalls of the inner chamber 31 and along its top Wall, being dischargedthrough the central opening 23 in the top Wall of the outer housing orshell.

In this manne-r the contents of such chamber are heatedup to andmaintained for the desired period at the required temperature,substantial fluctuations in the lat-ter being prevented by the automaticthermostatic control of the flow of gas to the burner.`

It will be observed that there is more or less of a dead air spacebetween the walls Q6 and 37 and between the latter and the removabledeck plates 68, whereby the Flasks will not be unduly heated from belowbut will be subjected to a practically uniform temperature on all sides.

The holes 34 in conjunction with the aperture Q3 afford convenient andsimple means for ventilating and permitting the esca-pe of moisture fromthe heat chamber containing the flasks.

The invention, as defined by the appended claim, is susceptible of avariety of embodiments and hence more or less radical changes may bemade in the structure illustrated and described without departure fromthe substance and essence of the invention and without the sacrifice ofany of its substantial benefits and advantages.

I claim:

An oven of the character described, comprising in combination, a housinghaving apertured top and bottom walls, legs supporting said housing, thefront Wall of said housing having upper and lower doorways and doorstherefor, a gas-burner supported on said bottom wall, a horizontalpartitionwall in said housing between said doorways leaving a space`between itself and the end and back walls of said housing, a chamberabove said partition-wall .having its top, rear, and end walls spacedinwardly from the corresponding walls of said housing and its bottomwall spaced above said partition- "all, the top wall of said chamberbeing a-pertured for ventilation, the lower door of said housingaffording access to the compartment containing the gas-burner, the upperdoor affording access to said chamber, a heat deflector secured belowsaid partition-Wall above said burner, a. deck plate in said chamberhaving downturned marginal fianges resting on the bottom wall thereof, athermostat in said chamber, a gas pipe connection with said burner, anda valve in said connection controlled by said thermostat.

EUGENE MAGINNIS.

